The invention relates to a data transfer control unit located between a memory unit and one or more peripheral units.
In information processing systems, a data transfer control unit is provided between a memory unit and one or more peripheral units (e.g., a disk drive) to control data transfer between the memory unit and the peripheral units. In a typical data transfer operation, a peripheral unit sends a transfer request command to the data transfer control unit which then issues a memory request command to the memory unit. In response to the memory request command, the memory unit performs either a read or a write operation processing depending on the contents of the transfer request command and then sends reply information to the control unit.
However, prior art data transfer control units have no adequate fault detection capability to detect various faults which may occur in the memory unit. Faults which may occur in the memory unit include the following: the operation required by a transfer request command given from the peripheral unit was not performed in the memory unit; a command disappearance took place in the memory unit; and a plurality of pieces of reply information were issued from the memory unit in response to a single memory request command.